The focus of these studies has been on the functional role of the MHC class I molecule and the development of model systems for examining this function both in vitro and in vivo. Specific accomplishments during the past year include: 1) quantitative measurement of the interaction of MHC class I molecules-peptide complexes with T cell receptors; 2) the evaluation of the role of the MHC class I molecule H-2Dd in the signalling of a subset of NK cells bearing the cell surface marker Ly-49; 3) the quantitative evaluation and mathematical modeling of the contribution of MHC and peptide to T cell stimulation; and 4) the production of single chain MHC class I molecules for functional and binding studies.